Storage system and storage system data migration method

ABSTRACT

This storage system modifies the migration plan in accordance with the state of the migration destination when a plurality of volumes are migrated all at once. Migration-source volumes are migrated collectively to volumes inside the migration-destination storage apparatus. The user can make settings related to migration-source volumes and migration-destination volumes in a migration plan, and can establish a mid-process control plan for modifying the migration plan in the middle of processing. If a failure occurs in the migration-destination storage apparatus subsequent to the commencement of data migration processing, a processing method controller either cancels or temporarily halts the data migration processing, or changes the migration destination, on the basis of the mid-process control plan. When changing the migration destination, a previously selected alternate storage apparatus is selected as the new migration-destination storage apparatus. When a failure occurs in the alternate storage apparatus, yet another alternate storage apparatus is selected.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application relates to and claims priority from Japanese PatentApplication No. 2006-110494 filed on Apr. 13, 2006, and is acontinuation of U.S. application Ser. No. 12/873,432, filed Sep. 1, 2010now U.S. Pat. No. 7,996,640; which is a continuation of U.S. applicationSer. No. 12/269,164, filed Nov. 12, 2008, now U.S. Pat. No. 7,805,585;which is a continuation of U.S. application Ser. No. 11/445,202, filedJun. 2, 2006, now U.S. Pat. No. 7,469,325, the entire disclosures ofwhich are incorporated herein by reference.

BACKGROUND

The present invention relates to a storage system and a storage systemdata migration method.

In recent years, the disk capacity of a storage apparatus, whichprovides a data storage region, has been increased in line with thelarger amounts of data being processed by a host computer (hereinafter,“host”). A storage apparatus creates a pool region from a plurality ofphysical disk storage regions, extracts from this pool region a storageregion of a capacity required by a host to create a logical volume, andprovides this logical volume to the host. The host writes and reads datato and from this logical volume.

Although there are differences according to the type of data, generallyspeaking, the utility value of data decreases with the passage of time,and little used data is stored in a logical volume. If an expensive diskis used to create a logical volume utilized by a host, data of littleutility value will be wastefully stored in the storage region of anexpensive disk, and the cost-effectiveness of the disk will be reduced.

Further, for example, according to the law, there are situations inwhich data, such as electronic mail and medical data, must be maintainedfor a fixed period of time or longer, even, for example, when it is lowuse data. When an expensive disk is used as the storage destination fordata to be stored over a long period of time, as described hereinabove,the cost-effectiveness of the disk decreases, and the operational costof the storage apparatus rises. With this sort of problem in mind,technology for migrating data from an expensive disk to a low-cost diskhas been proposed (Japanese Laid-open Patent No. 2000-293317, U.S. Pat.No. 6,108,748, Japanese Laid-open Patent No. 2003-140836, and JapaneseLaid-open Patent No. 2003-345522).

In the above-mentioned prior art, data can be moved by copying data fromone disk to another disk. A user, for example, selects amigration-source storage apparatus and a migration-destination storageapparatus, and devises a data migration plan for the purpose ofimproving the cost-effectiveness of a disk, and enhancing the responseperformance of high-use data. Here, for example, when migration isperformed simultaneously to a plurality of associated volumes, as withvolumes that form a copy pair, data migration must be completed bymaintaining this association as-is.

However, since the state of a storage apparatus changes in various ways,there is no guarantee of achieving results that correspond to theinitial data migration plan. For example, in the case of a storagesystem that is required to operate non-stop 24-hours-a-day,365-days-a-year, data will be migrated as the storage apparatus isoperating. Therefore, data migration is carried out under an environmentin which the states of the components of a storage apparatus(controller, cache memory, and so forth) change in various ways.

If a failure of some sort should occur in the migration-destinationstorage apparatus during data migration, for example, even if datamigration processing is capable of continuing at the time the failureoccurs, there will be occasions when the results anticipated by theinitial data migration plan will not be achievable thereafter due to thesecondary effects of the failure. For example, despite the fact thatdata migration was executed for the purpose of improving responseperformance, if the load on the data migration-destination storageapparatus rises, there are times when the anticipated responseperformance cannot be achieved following completion of the datamigration. In this case, a user must go to the added trouble of devisinga new data migration plan for realizing the initially anticipatedresponse performance, and re-migrating the data.

Further, it is also possible that data migration processing will failpart way through due to the failure that occurred in themigration-destination storage apparatus. In this case as well, just asdescribed hereinabove, a user must create a new data migration plan andcarry out data migration processing.

In addition, the migration of data respectively to a plurality ofmigration-destination storage apparatuses can also be considered, but ifdata migration to any one of these migration-destination storageapparatuses fails, a user must execute data migration by creating a datamigration plan all over again. When carrying out a data migration, auser devises a data migration plan, sets up the storage apparatusesaccording to this plan, and waits for data copying to be completed.Therefore, carrying out repeated data migrations to the samemigration-targeted volume reduces customer satisfaction. Thus, in theprior art, data migration that takes into consideration the fluctuatingstate of a storage apparatus is not examined, and as such, is not veryuser-friendly.

SUMMARY

With the foregoing in mind, an object of the present invention is toprovide a storage system and storage system data migration method thatcan enhance the ease-of-use of a user when migrating data to a pluralityof volumes as a group. Another object of the present invention is toprovide a storage system and storage system data migration method thatcan automatically modify an initial migration plan in accordance withthe state of a migration destination when migrating data to a pluralityof volumes as a group. Yet other objects of the present invention shouldbecome clear from the disclosure of the embodiments, which will beexplained hereinbelow.

A storage system, which accords with a first aspect of the presentinvention, and solves for the above-mentioned problems, is a storagesystem, which comprises a plurality of storage apparatuses each havingat least one logical volume, the storage system comprising a datamigration processor for selecting at least one of the respective storageapparatuses as a migration-source storage apparatus, selecting at leastone of the respective storage apparatuses as a migration-destinationstorage apparatus, and executing data migration processing for migratinga plurality of logical volumes as a group from the migration-sourcestorage apparatus to the migration-destination storage apparatus; amonitoring unit for monitoring the state of at least onemigration-destination storage apparatus; and a processing methodcontroller for controlling the processing method of data migrationprocessing based on the state of at least one migration-destinationstorage apparatus monitored by the monitoring unit.

In an embodiment of the present invention, a processing methodcontroller comprises a plurality of respectively different processingmethods, and controls the processing method of data migration processingby selecting any one processing method from among the plurality ofprocessing methods.

In an embodiment of the present invention, a processing methodcontroller comprises a plurality of respectively different processingmethods, and, when the state of a migration-destination storageapparatus coincides with a pre-set execution condition, controls theprocessing method of data migration processing midway through the datamigration processing by selecting, from among the plurality ofprocessing methods, a processing method that is made correspondent tothe execution condition beforehand.

In an embodiment of the present invention, a processing methodcontroller comprises a plurality of respectively different processingmethods, and an execution condition, which is defined by making thestate of a migration-destination storage apparatus and the progress ofdata migration processing correspondent to a processing method selectedfrom among the plurality of processing methods, is set beforehand, andthe processing method controller controls the processing method of datamigration processing midway through the data migration processing byselecting the processing method defined by the execution condition whenthe state of a migration-destination storage apparatus and the progressof the data migration processing coincide with the execution condition.

In an embodiment of the present invention, the plurality of processingmethods comprise at least a first processing method for canceling datamigration processing; a second processing method for interrupting datamigration processing; and a third processing method for changing amigration-destination storage apparatus to an alternate storageapparatus selected from among the respective storage apparatuses, andallowing data migration processing by the data migration processor tocontinue.

An embodiment of the present invention is constituted such that themonitoring unit monitors the states of storage apparatuses other thanthe migration-destination storage apparatus, and the processing methodcontroller selects an alternate storage apparatus based on the states ofthe other storage apparatuses when the third processing method is madecorrespondent to the execution condition.

In an embodiment of the present invention, the alternate storageapparatus is defined beforehand in the execution condition, themonitoring unit monitors the respective states of themigration-destination storage apparatus and the alternate storageapparatus, and the processing method controller determines whether ornot it is possible to switch from the migration-destination storageapparatus to the alternate storage apparatus based on the state of thealternate storage apparatus when the state of the migration-destinationstorage apparatus coincides with the execution condition, and when it isdetermined that switching is possible, changes the migration-destinationstorage apparatus to the alternate storage apparatus.

In an embodiment of the present invention, the plurality of logicalvolumes targeted for data migration processing by the data migrationprocessor have an association with one another, and when the processingmethod controller determines that it is not possible to switch from themigration-destination storage apparatus to the alternate storageapparatus, it generates, inside the migration-source storage apparatus,a copy volume of either all or a portion of a logical volume of thelogical volumes having the association, and establishes the associationin the copy volume.

In an embodiment of the present invention, the alternate storageapparatus is defined beforehand in the execution condition, themonitoring unit respectively monitors the states of themigration-destination storage apparatus, the alternative storageapparatus, and another storage apparatus, and the processing methodcontroller, (1) when the state of a migration-destination storageapparatus coincides with an execution condition, determines whether ornot it is possible to switch to the alternate storage apparatus based onthe state of the alternate storage apparatus; (2) when it has beendetermined that switching to the alternate storage apparatus ispossible, switches from the migration-destination storage apparatus tothe alternate storage apparatus; and (3) when it has been determinedthat switching to the alternate storage apparatus is not possible,selects a new alternate storage apparatus based on the state of anotherstorage apparatus being monitored by the monitoring unit, and switchesthe migration-destination storage apparatus to the newly selectedalternate storage apparatus.

In an embodiment of the present invention, the processing methodcontroller, prior to switching the migration-destination storageapparatus to either the alternate storage apparatus or the new alternatestorage apparatus, requests approval regarding the propriety ofswitching, and when approval is forthcoming, switches from themigration-destination storage apparatus to either the alternate storageapparatus or the new alternate storage apparatus.

In an embodiment of the present invention, the monitoring unitrespectively monitors the states of the migration-source storageapparatus and the migration-destination storage apparatus, and, when thethird processing method is made correspondent to the executioncondition, the processing method controller treats either themigration-source storage apparatus or the migration-destination storageapparatus, whichever has the least load, as the migration source, andre-migrates data, which has already been migrated to themigration-destination storage apparatus, to the alternate storageapparatus.

In an embodiment of the present invention, the monitoring unit isconstituted so as to monitor, as the state of at least themigration-destination storage apparatus, the load state, the cachememory usage state, and the fault status of the migration-destinationstorage apparatus.

In an embodiment of the present invention, an execution condition can beset for each of a plurality of states of the migration-destinationstorage apparatus.

A storage system according to another aspect of the present invention isa storage system, which comprises a plurality of storage apparatuseseach having at least one logical volume, and a management apparatus formanaging these respective storage apparatuses, the storage systemcomprising a data migration processor for selecting at least one of therespective storage apparatuses as a migration-source storage apparatus,selecting at least one of the respective storage apparatuses as amigration-destination storage apparatus, and executing data migrationprocessing for migrating a plurality of logical volumes as a group fromthe migration-source storage apparatus to the migration-destinationstorage apparatus; a monitoring unit for monitoring the state of atleast one migration-destination storage apparatus; and a processingmethod controller for controlling the processing method of datamigration processing based on the state of at least onemigration-destination storage apparatus monitored by the monitoringunit, and the monitoring unit and processing method controller arerespectively disposed in the management apparatus, and the datamigration processor is disposed in at least a migration-source storageapparatus.

A data migration method of a storage system according to yet anotheraspect of the present invention is a data migration method for migratingdata from a migration-source storage apparatus to amigration-destination storage apparatus in a storage system comprising aplurality of storage apparatuses, the data migration method respectivelyexecuting the steps of detecting the state of the migration-destinationstorage apparatus; commencing data migration processing for migrating avolume group comprising a plurality of logical volumes having anassociation with one another from the migration-source storage apparatusto the migration-destination storage apparatus; determining whether ornot the state of a migration-destination storage apparatus satisfies apreset execution condition; and changing the processing method of datamigration processing midway through the data migration processing, whenit has been determined that the state of a migration-destination storageapparatus satisfies the execution condition.

There will be cases when either all or a portion of the functions, meansand steps of the present invention, for example, can be constituted as acomputer program executed by a microcomputer. Then, this computerprogram, for example, can be affixed on a storage medium, such as a harddisk, optical disk, or semiconductor memory, and distributed. Or, thecomputer program can also be delivered via the Internet or other suchcommunication network.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing the concept of an embodiment ofthe present invention;

FIG. 2 is a schematic diagram showing the entire constitution of astorage system;

FIG. 3 is a block diagram focusing on the constitutions of a managementserver and host;

FIG. 4 is a block diagram focusing on the constitution of a storageapparatus;

FIG. 5 is a diagram schematically showing how volumes are moved inresource group units;

FIG. 6 is a schematic diagram showing the setup screen for setting amigration plan and a mid-process control plan;

FIG. 7 is a schematic diagram showing the constitution of a groupmanagement table;

FIG. 8 is a schematic diagram showing the constitution of a migrationmanagement table;

FIG. 9 is a schematic diagram showing the constitution of a migrationplan table;

FIG. 10 is a schematic diagram showing the constitution of a volumeattribute table;

FIG. 11 is a schematic diagram showing the constitution of a utilizationhistory table;

FIG. 12 is a schematic diagram showing an alternate storage apparatuscandidate table;

FIG. 13 is a flowchart showing a migration plan setting process;

FIG. 14 is a flowchart showing the process for acquiring performanceinformation in FIG. 13;

FIG. 15 is a flowchart showing the migration group setting process inFIG. 13;

FIG. 16 is a flowchart showing the data migration management process;

FIG. 17 is a flowchart showing data migration processing;

FIG. 18 is a flowchart showing the processing when a failure occurs inthe migration-destination storage apparatus during data migration;

FIG. 19 is a flowchart showing the mid-process control process;

FIG. 20 is a flowchart showing the process for changing the migrationdestination in FIG. 19;

FIG. 21 is a flowchart showing the processing when a load increase isdetected in the migration destination during data migration;

FIG. 22 is a schematic diagram showing the entire constitution of astorage system related to a second embodiment;

FIG. 23 is a flowchart showing the processing when a failure occurs inthe migration-destination storage apparatus during data migration;

FIG. 24 is a schematic diagram showing the entire constitution of astorage system related to a third embodiment;

FIG. 25 is a schematic diagram showing the constitution of a volumeattribute management table;

FIG. 26 is a flowchart showing a change-migration-destination process;

FIG. 27 is a schematic diagram showing the entire constitution of astorage system related to a fourth embodiment; and

FIG. 28 is a flowchart showing a change-migration-destination processexecuted by a storage system related to a fifth embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of the present invention will be explained hereinbelow onthe basis of the figures. FIG. 1 is an overall concept diagram of thisembodiment. Details will be explained further below, but as shown inFIG. 1, the storage system of this embodiment, for example, can beconstituted comprising a plurality of storage apparatuses 1, 2, 3, 4, astorage state monitoring unit 5, a processing method controller 6, and ahost 7.

The respective storage apparatuses 1, 2, 3, 4, for example, eachcomprise a hard disk drive or other such storage device, and have atleast one logical volume, which is created using the storage region ofthe storage device. That is, storage apparatus 1 has logical volumes 1A,1B, storage apparatus 2 has logical volumes 2A, 2B, storage apparatus 3has logical volumes 3A, 3B, and storage apparatus 4 has logical volumes4A, 4B, respectively. Furthermore, in the explanation that follows,there will be times when a logical volume is abbreviated and called a“volume”.

Further, the storage apparatus 1 (migration-source storage apparatus)selected by a user as the migration source of data migration processingcomprises a data copying part 10. The data copying part 10 correspondsto a data migration processor.

The volumes 1A, 1B of the migration-source storage apparatus 1, forexample, are mutually associated, like volumes that form a copy pair.Furthermore, the association between the volumes is not limited to acopy pair. The constitution is such that the volumes 1A, 1B, which havethese associations, are grouped together as a resource group 1D, anddata migration is carried out simultaneously as a group. In thisexample, it is supposed that the migration-targeted volumes 1A, 1B aremigrated collectively to a migration-destination storage apparatus 2.

The storage state monitoring unit 5 corresponds to the “monitoringunit”. The storage state monitoring unit 5 (hereinafter, the “monitoringunit 5”) respectively monitors the states of all the other storageapparatuses 3, 4 in addition to the migration-destination storageapparatus 2. Further, the monitoring unit 5 can also monitor the stateof the migration-source storage apparatus 1.

For example, the presence or absence of a failure in the respectivestorage apparatuses 2, 3, 4, the state of the communication channel, theload state of the controller, the load state of the parity group, andthe state of usage of the cache memory can be cited as the monitoringtargets of the monitoring unit 5. That is, the monitoring unit 5, forexample, can comprise a performance monitoring unit 5A and a faultmonitoring unit 5B. The performance monitoring unit 5A monitorsinformation related to the performances of the respective storageapparatuses 2, 3, 4 (or the storage apparatuses 1 through 4). The faultmonitoring unit 5B monitors information related to a failure in therespective storage apparatuses 2, 3, 4 (or the storage apparatuses 1through 4).

The processing method controller 6 is for controlling the method of datamigration processing during data migration processing. The processingmethod controller 6, for example, is provided beforehand with threetypes of processing methods: “cancel”, “interrupt” and “change migrationdestination”. “Cancel” signifies the canceling of data migrationprocessing that has been started. “Interrupt” signifies the temporaryhalting of data migration processing that has been started. In thiscase, the data migration processing can be restarted after the passageof a predetermined period of time. “Change migration destination”signifies changing the data migration destination from the initiallyscheduled migration-destination storage apparatus to another storageapparatus.

In this embodiment, as will be described hereinbelow, the constitutionis such that, when a failure of some sort occurs in the initiallyscheduled migration-destination storage apparatus 2, the data migrationdestination is changed to either an alternate storage apparatus 3specified beforehand by the user, or another, newly selected alternatestorage apparatus 4.

Here, the monitoring unit 5 and the processing method controller 6 canbe disposed inside the storage apparatus 1 host 7. Or, the monitoringunit 5 and the processing method controller 6 can also be disposedinside a computer for management use (for example, the management server200 in FIG. 2). Or, a constitution, in which the monitoring unit 5 isprovided by being distributed among the respective storage apparatuses1, 2, 3, 4, and the processing method controller 6 is disposed in thehost 7 and management computer, is also acceptable.

The host 7, for example, is constituted as either a server computer or amainframe computer, and makes use of the volumes 1A, 1B of themigration-source storage apparatus 1.

A migration plan 8 is prepared by the user, and the contents of a planrelated to data migration processing are stored. For example, thestorage apparatus to be used as the migration-source storage apparatus,the storage apparatus to be used as the migration-destination storageapparatus, the volume to be moved, and when data migration is tocommence are set in the migration plan 8.

It should be noted here that the migration plan 8 of this embodimentcomprises a mid-process control plan 8A. A condition for changing themethod of commenced data migration processing midway through theprocessing, and a changing method are stored in the mid-process controlplan 8A. For example, settings can be made beforehand so that, when afailure occurs in the migration-destination storage apparatus 2 midwaythrough the data migration processing, the user can either “cancel” or“interrupt” this data migration processing, or allow the process toproceed via a “change migration destination”.

Further, taking the progress of the data migration processing intoconsideration, the user can also specify beforehand that the processingmethod of the data migration processing be changed. The progress of thedata migration processing, for example, signifies the rate at which thedata migration processing progresses. In this embodiment, considerationcan be given to the progress of the data migration processing in orderto change the processing method of the data migration processing duringdata migration processing.

For example, when a minor failure occurs in the migration-destinationstorage apparatus 2, the user can allow the data migration processing toproceed as-is when the data migration processing has reached a level ofcompletion that is greater than a predetermined value, and can either“cancel’ or “interrupt” the data migration processing when the datamigration processing has only progressed up to a point that is less thana predetermined value. Thus, for the same observed event in themigration-destination storage apparatus 2, the user can freely set howthe data migration processing method will be changed in accordance withthe progress of the data migration processing at that time.

As explained hereinabove, when the user sets a “change migrationdestination”, an alternate storage apparatus 3 is specified beforehandin the mid-process control plan 8A in order to switch over from themigration-destination storage apparatus 2. Accordingly, the processingmethod controller 6 changes the migration destination by taking intoaccount the state of the alternate storage apparatus 3 as well as thestate of the migration-destination storage apparatus 2.

In other words, when a failure occurs in the migration-destinationstorage apparatus 2, or the load on the migration-destination storageapparatus 2 increases, the processing method controller 6 can take intoaccount the state of the alternate storage apparatus 3, and make adetermination as to whether or not it is possible to switch themigration destination to the alternate storage apparatus 3. When itdetermines that switching is possible, the processing method controller6 switches the data migration destination of the data migrationprocessing from the initial migration-destination storage apparatus 2 tothe alternate storage apparatus 3.

In addition, the processing method controller 6 can also determine thestate of another storage apparatus 4 beside the alternate storageapparatus 3. Thus, for example, even when it is not possible to switchfrom the migration-destination storage apparatus 2 to the alternatestorage apparatus 3 due to a failure having occurred in the alternatestorage apparatus 3, it can propose that the user set the other storageapparatus 4 as a new alternate storage apparatus. When the user approvesthis proposal, the processing method controller 6 changes themigration-destination storage apparatus of the data migration processingto the new alternate storage apparatus 4.

Thus, in this embodiment, the states (performance, fault) of the storageapparatuses 2, 3, 4 (or, storage apparatuses 1 through 4) undermanagement are respectively checked while the data migration processingis being carried out. Then, when the user sets a “change migrationdestination” in the mid-process control plan 8A beforehand, theprocessing method controller 6 can propose an available storageapparatus as an alternate storage apparatus to the user based on theresults of the check (monitoring results) during the data migrationprocessing.

In this embodiment, the constitution is such that the processing methodof data migration processing can be changed midway through the datamigration processing based on the state of the migration-destinationstorage apparatus 2. Therefore, for example, when a failure occurs inthe migration-destination storage apparatus 2, or the load on themigration-destination storage apparatus 2 increases during the datamigration processing, it is possible to cancel a useless data migrationprocessing, to put the data migration processing on standby until afailure or overload on the migration-destination storage apparatus 2 hasbeen eliminated, or to carry out the data migration processing byswitching to an alternate storage apparatus 3. This makes it possible toreduce the time and trouble associated with redoing the data migrationprocessing, and to enhance the usability of the user. This embodimentwill be explained in more detail hereinbelow.

First Embodiment

FIG. 2 is a schematic diagram showing the entire constitution of astorage system. This storage system, for example, is constitutedcomprising one or a plurality of hosts 100, at least one managementserver 200, and a plurality of storage apparatuses 300, 400, 500.

A host 100, for example, is constituted as a server computer or amainframe computer, and reads and writes data using volumes provided bythe storage apparatuses 300, 400, 500.

The management server 200 is a computer, which corresponds to the“management apparatus”, and collects information from the respectivestorage apparatuses 300, 400, 500, and hosts 100, and manages themigration of data inside the storage system. This will be explained indetail hereinbelow.

The network composition will be explained. The hosts 100, for example,are respectively connected to the storage apparatuses 300, 400, 500 viaa network CN11 used for data input and output, such as a LAN (Local AreaNetwork) or a SAN (Storage Area Network).

The hosts 100, for example, are connected to the management server 200by way of a LAN or other such host management network CN 12. Further,the management server 200 is connected respectively to the storageapparatuses 300, 400, 500 via a LAN or other such storage managementnetwork CN 13.

Details of the respective storage apparatuses 300, 400, 500 will beexplained below, but the storage apparatuses 300, 400, 500, for example,are interconnected via a LAN, SAN or other such copying network CN 14.The storage system can be constituted comprising three or more storageapparatuses. As will be explained below, the storage system can comprisefour storage apparatuses, a migration-source storage apparatus, amigration-destination storage apparatus, an alternate storage apparatus,and an alternate storage apparatus candidate, but due to paperconstraints, only three storage apparatuses are shown in the figure.

Furthermore, the above-mentioned network composition is one example, butthe present invention is not limited to this. For example, the hostmanagement network CN 12 and the storage management network CN 13 canalso be integrated. That is, a constitution in which the hosts 100,storage apparatuses 300, 400, 500 and management server 200 areconnected to either one of the management networks is also acceptable.

Similarly, the constitution can also be such that the copying network CN14 is done away with, and data copying is carried out between storageapparatuses using either the data input/output network CN 11 or themanagement network CN 13.

Similarly, the constitution can also be such that the management server200 is connected to the data input/output network CN 11, and thecollecting of management information, the issuing of instructions, anddata copying are all executed using this network CN 11.

Next, details of the respective apparatuses of the storage system willbe explained. To expedite the explanation, the constitutions of a host100 and management server 200 will be explained first, and theconstitutions of the respective storage apparatuses 300, 400, 500 willbe explained thereafter.

FIG. 3 is a schematic diagram showing the constitutions of the storagesystem host 100 and management server 200. The constitution of a host100 will be explained. A host 100, for example, is constitutedcomprising a CPU (Central Processing Unit) 110; a memory 120; aninterface (“I/F” in the FIG. 190 for connecting to the host managementnetwork CN 12; and an interface 191 for connecting to the datainput/output network CN 11. These components 110, 120, 190, 191 areinterconnected via a bus 180.

The functionality exhibited by a host 100 is achieved by the CPU 110executing a program. Data and a program used by the CPU 110 are storedin the memory 120. In particular, the memory 120 stores an agent program121. The agent program 121 is a program executed by the CPU 110, and isa program for transferring host 100 information to the management server200.

Furthermore, in addition to the above-mentioned constitution, a host 100comprises a user interface for exchanging information with a user. Aninformation input apparatus such as a keyboard switch, and aninformation output apparatus such as a display are known as userinterfaces, but since these interfaces are not directly related to thepresent invention, they have been omitted from the figure.

The management server 200, for example, has a CPU 210; a memory 220; aninterface 290 for connecting to the host management network CN 12; andan interface 291 for connecting to the storage management network CN 13.These components 210, 220, 290, 291 are interconnected via a bus 280.The various below-described functions exhibited by the management server200 are achieved by the CPU 210 executing a program.

The memory 220 stores data and programs utilized by the CPU 210. Inparticular, the memory 220 stores a storage management program 221; aperformance monitoring program 222; a fault monitoring program 223; amigration control program 224; a group management program 225; amigration management program 226; a migration plan table 227; a volumeattribute table 228; a utilization history table 229; and an alternatestorage candidate table 230.

The storage management program 221 is a program executed by the CPU 210,and manages the configuration information of the storage apparatuses300, 400, 500. Configuration information refers to the disk driveconfiguration, and volume configuration of the respective storageapparatuses 300, 400, 500.

The performance monitoring program 222 is a program executed by the CPU210, and, for example, is a program for acquiring the performanceinformation of the respective components of a storage apparatus, such asthe controller loads of the respective storage apparatuses 300, 400, 500under the management of the management server 200, the cache memoryusage rate, and the logical volume usage rate.

The fault monitoring program 223 is a program executed by the CPU 210,and is a program for detecting a failure that occurs in the storageapparatuses 300, 400, 500, and determining the nature of the failure.

The migration control program 224 is a program executed by the CPU 210,and is a program for issuing migration processing control commands to astorage apparatus.

Next, the configurations of the respective tables 225 through 230 willbe explained first, and the constitutions of the storage apparatuses300, 400, 500 will be explained thereafter.

The group management table 225 is a table for defining a resource groupfor simultaneously migrating a plurality of volumes. An example of agroup management table 225 is shown in FIG. 7. The group managementtable 225, for example, is constituted from three columns: resourcegroup number 2251; parent resource group number 2252; and informationfor specifying a migration-source volume 2253.

A resource group number 2251, for example, is information for uniquelyspecifying a resource group constituted from associated volumes, like agroup of volumes, which form a copy pair. A parent resource group number2252 is information for uniquely specifying a group comprising aplurality of resource groups. That is, as will be explained hereinbelowtogether with FIG. 5, a plurality of resource groups inside the samestorage apparatus, or a plurality of resource groups inside differentstorage apparatuses can be put together into a single parent resourcegroup, and collectively migrated. Information for specifying amigration-source volume 2253 is constituted comprising an apparatus ID(identification information) for identifying a storage apparatus inwhich a migration-source volume exists, and a volume ID for identifyinga volume. For example, “SS1.01” is information, which combines anapparatus ID “SS1” with a volume ID “01”, and indicates that the volumespecified as volume ID “01” of the volumes disposed inside the storageapparatus specified as “SS1” is the migration-source volume.

The migration management table 226 is a table for managing the datamigration processing. As shown in FIG. 8, the migration management table226, for example, is constituted from nine columns: a resource groupnumber 2261; information 2262 for specifying a migration-source volume;information 2263 for specifying a migration-destination volume; amigration status flag 2264 for showing the state of progress ofmigration processing; information 2265 for identifying the hostconnected to the migration-source volume; and information 2266 forspecifying an alternate volume of an alternate storage apparatus whenchanging the migration-destination storage apparatus. Here, a “0” is setin the migration status flag when data migration is complete, and a “1”is set when data migration is in progress.

The migration plan table 227 is a table for describing the contents ofmid-process control processing executed midway through the datamigration processing. As shown in FIG. 9, the migration plan table 227,for example, is constituted from six columns: a resource group number2271; event type 2272; degree of progress 2273; nature of mid-processcontrol process 2274; and restart time 2275.

The number of a resource group targeted for data migration is recordedin the resource group number 2271. The event type 2272 is informationindicating the type of event observed in the migration-destinationstorage apparatus. As an event, a partial failure of the controller, apartial failure of a path, a partial failure of the power source, apartial failure of the cache memory, an increase in the load on thecontroller, and a failure of the migration-destination volume can becited. These respective events become the triggers for executingmid-process control processing.

The degree of progress 2273 is information indicating the state ofprogress of the data migration processing, and, for example, isspecified as a percentage. The degree of progress 2273, together withthe event type 2272, constitutes an “execution condition” for commencingmid-process control processing. For example, when the degree of progressis set at “100% or less” in the event of a “partial failure ofcontroller”, mid-process control processing commences when the event“partial failure of controller” is detected despite the degree ofprogress. In the example shown in FIG. 9, “change migration destination”is carried out as the mid-process control process. That is, when apartial failure of the controller occurs, the migration-destinationstorage apparatus is changed to the alternate storage apparatus, anddata migration processing is continued.

Various different degrees of progress can correspond to the same event,and the nature of mid-process control processing can be changed inaccordance with the degree of progress. For example, in the exampleshown in FIG. 9, when an event called “load increase greater than setvalue” is detected, if the degree of progress of data migrationprocessing is less than 50% at that time, the data migration processingis “canceled.” However, when the degree of progress of data migrationprocessing has already reached 51% or more when a “load increase greaterthan set value” event is detected, the data migration processing is“temporarily halted.” The waiting time until restart is set at “1 hour”.

Furthermore, a value can be set for the restart time 2275 only when the“temporary halt (interruption)” is set in the information 2274indicating the nature of the mid-process control process. That is, whena failure or overload state occurs in the migration-destination storageapparatus, the data migration processing is interrupted for only theprescribed time recorded in restart time 2275, and data migrationprocessing is restarted following the passage of the prescribed timeperiod.

The details of a mid-process control process to be executed during datamigration processing are stored in the nature of mid-process controlprocess 2274. A mid-process control process is control, which isexecuted while data migration processing is being carried out, andcontrol for changing the nature of the processing of commenced datamigration processing.

For example, “cancel”, “temporary halt (interruption)”, and “changemigration destination” can be cited as the nature of mid-process controlprocess 2274. “Cancel” signifies the canceling of data migrationprocessing that has been started. “Temporary halt” signifies temporarilyhalting the data migration processing that has been started, andrestarting it after the passage of the restart time. “Change migrationdestination” signifies continuing data migration processing afterchanging the storage apparatus currently selected as the migrationdestination to another storage apparatus (alternate storage apparatus).

The volume attribute table 228 is a table, which expresses the volumeconfiguration information of a storage apparatus related to datamigration processing. The volume attribute table 228, as shown in FIG.10, for example, is constituted from five columns: apparatus ID 2281;volume ID 2282; disk type 2283; RAID level 2284; and disk capacity 2285.

The utilization history table 229 is a table for describing the dynamicperformance information of a storage apparatus related to data migrationprocessing. As shown in FIG. 11, a utilization history table 229 isprepared for each targeted resource. For example, one utilizationhistory table 229A manages the controller load history of a storageapparatus, and is constituted from three columns: measurement date/time2291; apparatus ID 2292; and controller load 2293. One more utilizationhistory table 229B manages the cache memory usage rate history insteadof the controller load. Here, for example, the controller load and cachememory usage rate are shown in the figure, but the utilization historytable 229 is not limited to these, and, for example, can also managevolume usage and parity group load histories.

The alternate storage candidate table 230 is the table utilized whenchanging the migration-destination storage apparatus in accordance witha mid-process control process. Alternate storage apparatus candidatesare stored in the alternate storage candidate table 230. An alternatestorage apparatus is a storage apparatus selected anew when a failure orthe like occurs in the scheduled switchover destination storageapparatus (a new storage apparatus selected by a user) making itunusable. For example, an explanation will be given using M0 for themigration-source storage apparatus, M1 for the initialmigration-destination storage apparatus at data migration, M2 for theswitchover destination storage apparatus when a failure occurs in theinitial migration destination storage apparatus M1, and M3 for thealternate storage apparatus. At the point in time at which the datamigration processing commences, data is migrated from M0 to M1. When afailure or overload occurs in M1, data migration switches from M0 to M2.When a failure or the like occurs in M2 at the time of this switchover,rendering it unusable, M3 is selected in place of M2, and data is movedfrom M0 to M3.

As shown in FIG. 12, the alternate storage candidate table 230, forexample, comprises three columns: resource group number 2301; volume ID2302; and alternate volume candidate volume ID (array) 2303. Forexample, “SS5.01, SS6.01” in FIG. 12 indicate that a volume (volumeID=01) of a storage apparatus (apparatus ID=SS5), and a volume (volumeID=01) of a storage apparatus (apparatus ID=06) are storage volumecandidates.

Furthermore, in addition to the above-mentioned constitution, themanagement server 200 comprises a user interface for exchanginginformation with a user, but this user interface will be omitted fromthe explanation since it does not correspond to the gist of the presentinvention.

The constitution of the storage apparatuses 300, 400, 500 will beexplained by referring to FIG. 4. Focusing on the constitution of thestorage apparatus 300, this storage apparatus 300, for example,comprises a control apparatus 301; a controller 310; a memory 320; acache memory 330; a disk drive 340; and interfaces 390, 391, 392. Thesecomponents 310, 320, 330, 340, 390, 391, 392 are connected by a bus 380.

The interfaces 390, 391, 392 will be explained first. The interface 390is for connecting to the data input/output network CN 11, and theinterface 391 is for connecting to the storage management network CN 13.The interface 392 is for connecting to the copying network CN 14.

The control apparatus 301 is an apparatus for controlling the operationof the storage apparatus 300. The control apparatus 301, for example,comprises a controller 310; a memory 320; and a cache memory 330.

The controller 310 can constitute a plurality of CPUs, and processes aread access and a write access from a host 100 by reading in andexecuting a program stored in the memory 320. The controller 310comprises at least channel adapter functionality for sending andreceiving data to and from a host 100, and disk adapter functionalityfor sending and receiving data to and from a disk drive 340. Forexample, the control substrate for channel adapter use and the controlsubstrate for disk adapter use can be constituted separately, andchannel adapter functionality and disk adapter functionality can each beprovided on a single control substrate.

Further, the controller 310 achieves data copying functionality betweenvolumes by executing a data migration program 321 stored in the memory320. Inter-volume data copying can be broadly divided into copyingwithin the same chassis, and copying between different chassis. Volumecopying inside the same chassis is copying in which the copy-source(migration-source) volume and copy-destination (migration-destination)volume are disposed inside the same storage apparatus. Copying betweendifferent chassis is copying in which the copy-source (migration-source)volume and copy-destination (migration-destination) volume are disposedinside different storage apparatuses.

The memory 320 is also called a control memory, and in addition to theabove-mentioned data migration program 321, stores a program and varioustypes of control information for processing an access from a host 100.The cache memory 330 stores write data received from a host 100, andread data read out from a disk drive 340. Furthermore, the constitutioncan also be such that a portion of a common memory region is used as thememory 320, and the remainder is used as the cache memory 330.

The disk drive 340, for example, can be constituted as a hard diskdrive, a semiconductor memory drive, an optical disk drive, or amagneto-optic disk drive. Further, citing a hard disk drive as anexample, for instance, different types of drives, such as an FC (FibreChannel) disk, and SATA (Serial AT Attachment) disk, can be mixedtogether.

A logical volume (hereinafter “volume”) 342, which is a logical storageregion, can be provided by using the physical storage region of therespective disk drives 340. Furthermore, in the figure, a logical volumeis displayed as “LU” for convenience sake. A volume 342 can also becalled a logical storage device. When heightening fault tolerance byusing parity data, as with RAID 5, a parity group 341 is constitutedfrom a plurality of disk drives 340. A volume 342 is used by a host 100.

Either one or a plurality of volumes 342 can be formed in a single diskdrive 340, and a plurality of disk drives 340 can be used to form eitherone or a plurality of volumes 342.

As shown in FIG. 4, when a plurality of volumes 342 is prepared oncommon disk drives 340, there are cases in which a data access to onevolume 342 will impact a data access of another volume 342. That is, anincreased load on one volume 342 can cause the response performance ofanother volume 342 to decrease. In this case, it should be possible toimprove response performance by moving either the one volume 342 or theother volume 342 to a different disk drive.

For example, if we represent a disk drive with a high access frequencyas 340H, and a disk drive with a low access frequency as 340L, it shouldbe possible to improve the response performance of a logical volume 342by moving this logical volume 342 from disk drive 340H to disk drive340L.

The data migration processing will be carried out to improve this kindof responsiveness. However, there is no guarantee that the datamigration plan devised by a user will bear the desired result. This isbecause the state of a storage system is constantly fluctuating.Accordingly, in this embodiment, as will be explained hereinbelow, whencollectively migrating a plurality of volumes, a data migration plan iseither automatically or semi-automatically modified in accordance withthe dynamically changing state of the storage system.

Storage apparatus 400 can be constituted the same as storage apparatus300. That is, storage apparatus 400, for example, comprises a controlapparatus 401; a controller 410; a memory 420; a cache memory 430; adisk drive 440; and interfaces 490, 491, 492, and these components 410,420, 430, 440, 490, 491, 492 are connected by a bus 480.

Further, a data migration program 421 is stored in the memory 420, andthis program 421 is read into and executed by the controller 410. Inaddition, a volume 442 is formed using the storage region of a diskdrive 440.

Since storage apparatus 500 can have the same constitution as storageapparatus 300, a redundant explanation will be omitted. Furthermore, thebasic constitution of the storage apparatuses 300, 400, 500 can beshared in common, and the model, functionality and other detailedspecifications can differ. For example, a certain storage apparatus canbe constituted as a higher functionality storage apparatus than anotherstorage apparatus.

The data migration of a resource group will be explained using FIG. 5.In this embodiment, a resource group 801 is constituted from a pluralityof volumes 342, and data is migrated collectively as a resource group.Further, a plurality of resource groups 801 can constitute a parentresource group 800, and an entire parent resource group 800 can bemigrated. In other words, a sub-resource group can be set in thecontents of a resource group.

As shown in FIG. 5, for example, a parent resource group 800 can beconstituted from a plurality of resource groups 801 that exist insidethe migration-source storage apparatus 300, and the parent resourcegroup 800 can be migrated to a plurality of migration-destinationstorage apparatuses 400, 500 all at once. In this case, for example, oneresource group 801 can be moved to storage apparatus 400, and the otherresource group 802 can be moved to storage apparatus 500. Furthermore,the schematic diagram shown in FIG. 5 is for explaining a resource groupdata migration, and does not coincide with a specific example of thedata migration processing, which will be explained hereinbelow.

Next, the operation of the storage system will be explained. Firstly, anoverview of the data processing procedure will be explained. Prior tocommencing the data migration processing, the user will specify acontrol method for modifying data migration processing in mid-process inpreparation for the occurrence of a specified event during the course ofdata migration processing. This series of setup processes is called amigration plan, and that migration plan, which specifies the mid-processcontrol method of the data migration processing, is called a mid-processcontrol plan.

After a migration plan has been established by the user, data migrationprocessing is commenced. The management server 200 measures theperformance information of the respective storage apparatuses undermanagement in preparation for searching out an alternate storageapparatus when a failure occurs during data migration processing. Then,when a specified event occurs during data migration processing, theprocessing method of the data migration processing is controlledmid-process in accordance with a previously set mid-process controlplan.

FIG. 6 is a schematic diagram showing examples of the setup screens usedby a user in a setup operation. These setup screens G1, G2 are providedto the user from the management server 200. A data migration can beperformed as a resource group as described hereinabove. As shown in theupper portion of the main setup screen G1, both the migration-sourcestorage apparatus and the migration-destination storage apparatus arespecified. Furthermore, although not shown in the figure, a resourcegroup number and migration-destination volume ID are also specified atthe time the migration-source storage apparatus and themigration-destination storage apparatus are specified.

Further, in the main setup screen G1, a method for modifying the datamigration processing when a specified event occurs (a mid-processcontrol processing method) can be specified beforehand for each ofvarious specified events. For example, “partial failure ofmigration-destination storage apparatus”, “path failure inmigration-destination storage apparatus”, “failure ofmigration-destination storage apparatus”, and “increased load on paritygroup of migration-destination storage apparatus” can be cited asspecified events.

When the user operates the “set plan” button, processing moves to thesub-setup screen G2 for setting the countermeasure to a specified event(mid-process control processing method). This sub-setup screen G2 (itcan also be called the detailed setup screen) is provided for eachspecified event. In this sub-setup screen G2, the details of mid-processcontrol processing can be set in accordance with the degree of progressof the data migration processing.

The sub-setup screen G2 shows the various settings that can be made whenthe specified event “partial failure of migration-destination storageapparatus” occurs, such as canceling the data migration processing ifthe degree of progress is within the range of 0% to 50%, and temporarilyhalting the data migration processing when the degree of progress isgreater than 51%. Further, as shown at the bottom of the sub-setupscreen G2, it is also possible to make a setting that changes thestorage apparatus of the data migration destination in accordance withthe degree of progress of the data migration processing. Furthermore,the management server 200 can also check in advance to make sure thatconflicting settings have not been made for the same resource group.

FIG. 13 is a flowchart showing the procedure for a migration plansetting process carried out prior to commencement of the data migrationprocessing. Furthermore, the flowchart shows the procedure within ascope required for understanding and executing the present invention,but this procedure will differ from that of an actual program. The samealso holds true for the other flowcharts explained hereinbelow. In thefollowing explanation, a step will be annotated as “S”.

Further, although the operating unit of the respective flowchartshereinbelow will in fact be either the CPU or controller that executesthe control program stored in memory, for explanation purposes, therewill be times when either the management server 200 or the respectivestorage apparatuses 300, 400, 500 will be described as the operationunit.

First of all, the CPU 210 of the management server 200 respectivelychecks the performance (controller load, cache memory usage rate, volumeusage rate) of each storage apparatus under its management in accordancewith the sequence of the performance monitoring program 222, and storesthe collected performance information in the utilization history table229 (S11). The procedure for acquiring this performance information willbe explained together with FIG. 14 hereinbelow.

Next, a migration group setting process is carried out (S12). Thedetails of this migration group setting process will be explained belowtogether with FIG. 15. Furthermore, this embodiment will be explainedusing an example of when a resource group does not comprise asub-resource group, that is, when a parent resource group 800 is notestablished.

After completing the migration group setting process, the managementserver 200 provides the user with the migration plan setup screens G1,G2 described together with FIG. 6 (S13). The user utilizes the mainsetup screen G1 to set a migration plan (S14).

Next, the management server 200 determines whether or not “changemigration destination” has been selected as the mid-process control plan(S15). “Change migration destination”, as explained hereinabove, is aplan for continuing the data migration processing by switching from theinitial migration-destination storage apparatus set by the migrationplan to an alternate storage apparatus.

When “change migration destination” has been set by the user (S15: YES),the management server 200 acquires attribute information from the volumeattribute table 228 (S16). The management server 200 also acquiresdynamic performance information from the utilization history table 229(S17). Then, based on the information of the volume attribute table 228,the management server 200 presents the user with either one or aplurality of alternate volumes of the same constitution as themigration-destination storage apparatus (S18).

At this point, within a user-specified time period, the managementserver 200, for example, can also present the user with alternatevolumes in sequence from the one with the lowest load. By providing auser with this kind of additional information, the user is able toselect the volume with the lowest load as the alternate volume, therebyenhancing usability.

When an alternate storage apparatus (alternate volume) has been selectedby the user, the management server 200 registers the storage apparatusselected as the alternate migration destination in the migrationmanagement table 226 (S19).

In this embodiment, for explanation purposes, the example given is onein which storage apparatus 300 is the migration-source storageapparatus, storage apparatus 400 is the migration-destination storageapparatus, and storage apparatus 500 is the alternate storage apparatus.

Next, the management server 200 makes all the alternate storageapparatuses detected in S18 candidate alternate storage apparatuses, andsaves this information in the alternate storage candidate table 230(S20). That is, in preparation for a situation in which a failure occursin the alternate storage apparatus selected in the mid-process controlplan, the management server 200 targets the alternate storage apparatuscandidates for monitoring as well. By detecting the alternate storageapparatus candidates in advance at alternate storage apparatus setuptime like this, the mid-process control plan can be smoothly executedeven when it is not possible to switch over to the alternate storageapparatus.

The management server 200 determines whether or not the migration plansetup is complete (S21). When the migration plan setup is not finished(S21: NO), processing returns to S14, and the migration plan setupoperation is restarted. When the entire migration plan setup is finished(S21: YES), the management server 200 creates and saves a migration plantable 227. This ends pre-setup prior to the commencement of the datamigration processing.

FIG. 14 is a flowchart showing the details of the performanceinformation acquisition procedure described in S11 in FIG. 13. Themanagement server 200, for example, queries each of the storageapparatuses under its management as to controller load, cache usage(utilization rate), and the channel processor load rate (S31).Furthermore, a channel processor is a processor for controlling thesending and receiving of data to and from a host 100.

Next, when the management server 200 acquires performance informationfrom each of the respective storage apparatuses (S32), it makes theapparatus ID and acquisition time correspondent to this acquiredperformance information, and saves it to the utilization history table229 (S33).

FIG. 15 is a flowchart showing the details of the migration groupsetting process described in S12 in FIG. 13. First, the managementserver 200 determines if a volume targeted for migration(migration-source volume) was selected by the user (S41).

When a migration-source volume has been selected by the user (S41: YES),the management server 200 registers the selected migration-source volumein the group management table 225 (S42). The management server 200determines whether or not a parent resource group will be set (S43).That is, it determines whether or not a plurality of resource groupswill be put together into one resource group (a parent resource group),and migrated all at once.

When a parent resource group is to be set (S43: YES), the managementserver 200 determines whether or not a plurality of resource groups wasselected by the user (S44). When a plurality of resource groups has beenselected (S44: YES), the management server 200 registers a parentresource group, which will be constituted from the plurality of resourcegroups selected by the user, in the group management table 225 (S45).

The management server 200 determines whether or not the setup task forthe migration targeted group is complete (S46), and when it is notcomplete (S46: NO), it returns processing to S41. When the setup task bythe user is complete (S46: YES), this process ends. Furthermore, when aparent resource group is not established (S43: NO), S44 and S45 areskipped, and processing moves to S46.

FIG. 16 shows the processing procedure (the data migration processingmanagement procedure) when the data migration processing is started.First, the CPU 210 of the management server 200 issues a migration startcommand to each of the migration-source storage apparatus 300 and themigration-destination storage apparatus 400 according to the sequence ofthe migration control program 224 (S51).

Next, the management server 200 determines whether or not a migrationprocess start notification has been received from both themigration-source storage apparatus 300 and the migration-destinationstorage apparatus 400 (S52). The CPU 210 of the management server 200checks, either on a regular or irregular basis, the progress of the datamigration processing in accordance with the sequence of the storagemanagement program 221, and updates the migration management table 226as needed (S53).

The management server 200 determines if migration process complete hasbeen notified from the migration-source storage apparatus 300 (S54), andwhen a migration process complete notification is received from themigration-source storage apparatus 300 (S54: YES), it notifies the userto the effect that data migration processing is complete (S55).

However, when a migration start notification cannot be received fromboth the migration-source storage apparatus 300 and themigration-destination storage apparatus 400 (S52: NO), the managementserver 200 notifies the user of an error (S56). This is because datamigration processing could not be started.

Furthermore, the data migration processing complete notification anderror notification, for example, can be achieved by virtue of a messagedisplayed on a management server 200 terminal screen. Or, theconstitution can also be such that the user is notified using e-mail.

FIG. 17 is a flowchart showing data migration processing. This datamigration processing, for example, is executed by the migration-sourcestorage apparatus 300. Furthermore, the constitution can also be suchthat data is migrated by virtue of the migration-destination storageapparatus 400 reading the data from the migration-source storageapparatus 300.

The migration-source storage apparatus 300 determines whether or not amigration start notification (S51 of FIG. 16) was received from themanagement server 200 (S61). When a migration start notification wasreceived (S61: YES), the controller 310 of the migration-source storageapparatus 300 queries the migration-destination storage apparatus 400 asto whether or not data migration processing can commence in accordancewith the sequence of the data migration program 321 (S62).

The migration-source storage apparatus 300 (more specifically, thecontroller 310) determines whether or not to commence data migrationprocessing (S63). When it is determined that commencement of datamigration processing is possible (S63: YES), the migration-sourcestorage apparatus 300 sends a migration start notification to themanagement server 200 (S64).

The migration-source storage apparatus 300 reads out data from themigration-source volume, and transfers this read-out data to themigration-destination storage apparatus 400 (S65). Themigration-destination storage apparatus 400, after temporarily storingthe data received from the migration-source storage apparatus 300 in thecache memory 430, writes this data to the migration-destination volume.

The migration-source storage apparatus 300 makes a determination as towhether or not volume copying was completed, that is, whether or not allof the data of the migration-source volume was copied to themigration-destination volume (S66). S65 and S66 are repeatedly executeduntil data migration is complete for all the migration-source volumesconstituting a resource group.

When data migration is complete (S66: YES), the migration-source storageapparatus 300 sends a migration end notification to the managementserver 200 (S67). However, when the migration-source storage apparatus300 determines that data migration processing cannot commence (S63: NO),the migration-source storage apparatus 300 notifies the managementserver 200 of an error (S68).

FIG. 18 is a flowchart showing the processing procedure when a failureoccurs in the migration-destination storage apparatus 400 while datamigration processing is being executed. This processing is executed bythe management server 200.

First, the management server 200 determines whether or not a failurenotification was received from the migration-destination storageapparatus 400 (S71). As types of failures, for example, partial failureof the controller 410, partial failure of the cache memory 430, partialfailure of a volume 450, and partial failure of the power source can becited.

When a failure notification is received from the migration-destinationstorage apparatus 400 (S71: YES), the management server 200 determinesthe type of failure based on the information received from themigration-destination storage apparatus 400 (S72). The management server200, on the basis of the type of failure determined and the migrationplan table 227, queries the user as to the propriety of executing themid-process control process set relative to this failure (S73).

When the user gives instructions for the mid-process control process tobe executed (S74: YES), that is, when changing the data migrationprocessing midway through that processing is approved by the user, themanagement server 200 executes mid-process control processing (S75).Changing the data migration processing method during a data migrationwill be explained hereinbelow together with FIG. 19.

By contrast, when the user does not give instructions to executemid-process control processing (S74: NO), the management server 200continues data migration processing as-is without carrying out thepre-set mid-process control process (S76).

Next, FIG. 19 is a flowchart showing the procedure of the mid-processcontrol process described in S75 in FIG. 18. First, the managementserver 200 determines whether or not the type of mid-process controlprocess (the nature of the mid-process control process) selectedbeforehand by the user is “cancel” (S81).

When the user has specified in advance to cancel the data migrationprocessing (S81: YES), the management server 200 instructs themigration-source storage apparatus 300 and migration-destination storageapparatus 400 to stop (cancel) data migration processing (S82).

When the mid-process control process selected by the user is not“cancel” (S81: NO), the management server 200 determines whether or notthe mid-process control process selected by the user is “temporary halt”(S83).

When the user has specified in advance to temporarily halt the datamigration processing (S83: YES), the management server 200 instructs themigration-source storage apparatus 300 and migration-destination storageapparatus 400 to temporarily halt data migration processing (S84). Then,after instructing the temporary halt, the management server 200 waitsfor the prescribed restart time to elapse (S85), and when the restarttime has elapsed (S85: YES), it instructs the migration-source storageapparatus 300 and migration-destination storage apparatus 400 to restartdata migration processing (S86).

When the user-specified mid-process control processing method is neither“cancel” nor “temporary halt” (S83: NO), the management server 200executes “change migration destination processing” (S87). This changemigration destination process will be explained hereinbelow togetherFIG. 20.

FIG. 20 is a flowchart showing the details of the change migrationdestination processing described in S87 in FIG. 19. In change migrationdestination processing, when the initially scheduledmigration-destination storage apparatus cannot be utilized, themigration destination is switched to the alternate storage apparatus500, or to another different alternate storage apparatus, and datamigration processing is continued.

First, the management server 200 determines whether or not a failure hasoccurred in the previously registered alternate storage apparatus 500(S91). That is, it makes a determination as to whether or not thealternate storage apparatus 500 can be used as the newmigration-destination storage apparatus.

When a failure has not occurred in the previously registered alternatestorage apparatus 500 (S91: NO), the management server 200 completesdata migration for the volume undergoing data migration (S92). Next, themanagement server 200 overwrites the “migration-destination volume” inthe migration management table 226 to reflect the alternate volume ofthe alternate storage apparatus 500 (S93).

The management server 200 measures the respective controller loads ofthe initially set migration-destination storage apparatus 400 andmigration-source storage apparatus 300 (S94). When the load of themigration-source storage apparatus 300 is lower than that of themigration-destination storage apparatus 400 (S95: YES), the managementserver 200 migrates a migrated volume from the migration-source storageapparatus 300 to the alternate storage apparatus 500 (S96). By contrast,when the load of the migration-destination storage apparatus 400 islower than that of the migration-source storage apparatus 300 (S95: NO),the management server 200 migrates a migrated volume from themigration-destination storage apparatus 400 to the alternate storageapparatus 500 (S97).

That is, for a volume that has already been migrated to themigration-destination storage apparatus 400, data is copied from eitherthe migration-source storage apparatus 300 or the migration-destinationstorage apparatus 400, whichever one has the least controller load, tothe alternate storage apparatus 500.

However, when a failure occurs in the alternate storage apparatus 500previously selected by the user, and this alternate storage apparatus500 cannot be utilized (S91: NO), the management server 200 determineswhether or not an alternate volume candidate is registered in thealternate storage candidate table 230 (S98).

When an alternate volume candidate exists (S98: YES), and a plurality ofstorage apparatuses are listed as candidates in the alternate storagecandidate table 230, the management server 200 detects from among theseplurality of candidates the storage apparatus with the best performance(S99).

The management server 200 presents this detected storage apparatus tothe user, and queries the user if this newly detected alternate storageapparatus can be used in place of alternate storage apparatus 500(S100).

When approval for the change is obtained from the user (S101: YES),processing moves to S92, and data migration processing is carried outusing the new alternate storage apparatus as described hereinabove (S92through S97). When approval is not obtained from the user (S101: NO),the management server 200 cancels data migration processing (S102).Further, when there is not even one alternate volume candidate (S98:NO), the management server 200 cancels data migration processing (S102).

FIG. 21 is a flowchart showing the processing procedure when the load onthe migration destination storage apparatus 400 increases during datamigration processing. The management server 200 determines whether ornot the controller load of the migration destination storage apparatushas risen, or whether or not the load (disk I/O) of the parity group 441to which the migration-destination volume 442 belongs has increased(S111).

Then, when a controller or parity group load increase is detected (S111:YES), the management server 200 queries the user as to the propriety ofexecuting mid-process control processing (S112). When the user instructsthe execution of mid-process control processing (S113: YES), themid-process control processing described in FIG. 19 and FIG. 20 isexecuted (S114).

By contrast, when the user does not instruct the execution ofmid-process control processing (S113: NO), that is, when the user doesnot desire that mid-process control processing commence, the managementserver 200 continues the current data migration processing as-is withoutmodification (S115).

Since this embodiment is constituted as described hereinabove, thefollowing effect is achieved. In this embodiment, the constitution issuch that the data migration processing method can be modified orchanged in the middle of data migration processing on the basis of thestate of the migration-destination storage apparatus 400. Therefore, itis possible to prevent useless data migration processing from beingexecuted as-is, or to prevent a situation in which the desired result isnot obtained subsequent to data migration.

In addition, after a user ascertains that the initial migration plan hasfailed, there is no need to devise and re-set a new migration plan. Bysimply setting a mid-process control plan beforehand, the user canachieve the desired data migration in a dynamically changing storagesystem. Thus, this embodiment can improve the workability of datamigration processing, and can enhance user ease-of-use.

In the present invention, at the point in time when the user selects thealternate storage apparatus 500, all candidate storage apparatusescapable of being used in place of the alternate storage apparatus 500are detected in advance, and the performance information of thesecandidate storage apparatuses (candidates for alternate storageapparatus) is collected ahead of time. Therefore, even when it is notpossible to switch from the migration-destination storage apparatus 400to the alternate storage apparatus 500, another alternate storageapparatus can rapidly be proposed to the user, thereby enhancingusability.

In this embodiment, for a migrated volume, either the migration-sourcestorage apparatus 300 or the migration-destination storage apparatus400, whichever has the least controller load, is selected, and analready migrated volume is migrated to the alternate storage apparatus.Therefore, the load inside the storage system can be balanced, making itpossible to prevent load from concentrating in a specific storageapparatus.

In this embodiment, a plurality of volumes can be collected togetherinto a resource group, and migrated collectively at the same time.Therefore, for example, a plurality of mutually associated volumes, likea plurality of volumes in a copy pair relationship, can be migratedsimultaneously, enhancing usability.

In particular, when a group of a plurality of associated volumes iscollectively subjected to data migration, it is apt to take a long timebefore the data migration processing is complete. However, in a storagesystem that is capable of continuous operation 24 hours a day, 365 daysa year, the state of the storage system changes from one minute to thenext. Therefore, there is no guarantee that the state of the storagesystem when the migration plan was devised will continue subsequent tothe completion of data migration processing. Accordingly, in thisembodiment, in order to carry out data migration for a group of aplurality of associated volumes in a storage system whose state changesin various ways, performance information regarding themigration-destination storage apparatus 400 and alternate storageapparatus 500, as well as the alternate storage apparatus candidates iscollected on a regular basis, and data migration processing is modifiedas needed in accordance with the state of the migration-destinationstorage apparatus 400. This increases the likelihood of being able toachieve user-desired data migration in a storage system comprising aplurality of storage apparatuses 300, 400, 500, . . . , and thusenhances usability.

In this embodiment, all alternate volume candidates are extracted inadvance prior to commencing the data migration processing. That is, ofthe volumes available at the start of data migration processing, allthose volumes available as migration-destination volumes are extracted.Instead of this, the constitution can also be such that an alternatevolume is newly created when searching for an alternate volume. However,in this case, it takes time until the switch to the alternate volume ismade, generating temporal gaps in the flow of processing for datamigration, and making it impossible to carry out rapid data migration.By contrast, in this embodiment, because alternate volume candidates areextracted beforehand and monitored by the management server 200, it ispossible to rapidly switch the migration destination and continue datamigration processing even when a failure occurs in the alternate storageapparatus 500.

Second Embodiment

A second embodiment of the present invention will be explained based onFIGS. 22 and 23. In this embodiment, a group of migration-sourcevolumes, which are distributed and arranged in a plurality of storageapparatuses, is migrated all at once to a plurality ofmigration-destination storage apparatuses. Since each of the followingembodiments, to include this embodiment, correspond to variations of theabove-mentioned first embodiment, redundant explanations will beomitted, and the focus will be on explaining the points of differencewith the first embodiment.

FIG. 22 is a schematic diagram showing the overall constitution of astorage system according to this embodiment. This storage system has aplurality of hosts 100 (only one is shown in the figure), a managementserver 200A, and a plurality of storage apparatuses 300, 400, 500, 600,700. Furthermore, this embodiment can also comprise other storageapparatuses besides the storages apparatuses 300, 400, 500, 600, 700shown in the figure.

The points of difference with the first embodiment are the addition ofstorage apparatuses 600, 700, and the fact that a resource group isdefined as spanning a plurality of storage apparatuses 300, 400.

The added storage apparatuses 600, 700, like the other storageapparatuses 400, 500, can basically be constituted the same as storageapparatus 300, and comprise control apparatuses 601, 701. Further, therespective storage apparatuses 600, 700 are connected to the otherstorage apparatuses 300, 400, 500 via a network for copying CN14. Thedetails of the storage apparatuses 600, 700 will be omitted.

In this embodiment, storage apparatus 300 and storage apparatus 400constitute migration-source storage apparatuses. That is, a parentresource group 800A is constituted from a resource group 801A providedin a first migration-source storage apparatus 300, and a resource group801A provided in a second migration-source storage apparatus 400. Therespective volumes 342, 442 belonging to this parent resource group 800Aconstitute migration-source volumes.

Storage apparatuses 500 and 600 constitute migration-destination storageapparatuses. The migration-destination volumes become volume 542 ofstorage apparatus 500, and volume 642 of storage apparatus 600.

The alternate storage apparatus is storage apparatus 700. The alternatevolume becomes volume 742 of storage apparatus 700.

FIG. 23 shows the processing procedure when a failure is detected ineither of migration-destination storage apparatus 500 ormigration-destination storage apparatus 600 during data migration. TheCPU 210 of the management server 200A checks for failures in themigration-destination storage apparatuses 500, 600 in accordance withthe sequence of the fault monitoring program 223 (S121).

When a failure notification is received from eithermigration-destination storage apparatus 500 or migration-destinationstorage apparatus 600 (S121: YES), the management server 200A specifiesthe type of failure, the parent resource group related to this failure,and the respective resource groups constituting the parent resourcegroup (S122).

Then the management server 200A queries the user as to whether or not toexecute the mid-process control process registered in the migration plantable 227 for all resource groups (S123). When the user instructsmid-process control processing (either the canceling or temporaryhalting of data migration processing, or the changing of the migrationdestination) for all resource groups regardless of whether or not theyare related to the failure of the migration-destination storageapparatuses 500, 600 (S124: YES), the management server 200A executesmid-process control processing for each resource group (S125).

The management server 200A repeatedly executes S125 until the pre-setmid-process control processing is complete for all the resource groups(S126). After mid-process control processing has been executed for allresource groups (S126: YES), the management server 200A continues datamigration processing in accordance with the modified migration plan(S127).

By contrast, when the user does not desire uniform mid-process controlprocessing for all resource groups (S124: NO), but rather only wantsmid-process control processing for the resource group related to thefailure (S128: YES), mid-process control processing is only executed forthe pertinent resource group (S129). After mid-process controlprocessing has been completed for the failure-related resource group inthe migration-destination storage apparatus, the management server 200Acontinues data migration processing in accordance with this modifiedmigration plan (mid-process control plan) (S130).

Furthermore, when the user does not desire to execute mid-processcontrol processing (S128: NO), the management server 200A continues thecurrent data migration processing as-is without executing mid-processcontrol processing (S131). That is, in this case, data migration iscarried out in accordance with the contents of the initial plan.

This embodiment, which is constituted in this manner, also demonstratesthe same effects as the above-mentioned first embodiment. In addition tothat, in this embodiment, a plurality of migration-source volumes 342,442 distributed in a plurality of storage apparatuses 300, 400 can bemigrated all at once to a plurality of storage apparatuses 500, 600,thereby further enhancing usability.

Third Embodiment

A third embodiment of the present invention will be explained based onFIGS. 24 through 26. In this embodiment, forming a local copy 442A of avolume inside the migration-source storage apparatus 400 will appear toa host 100 as if data migration has been completed.

This embodiment comprises a plurality of hosts 100 (only one is shown inthe figure), a management server 200B, and a plurality of storageapparatuses 300, 400, 500, 600, 700 the same as the above-mentionedsecond embodiment. Also similar to the above-mentioned secondembodiment, a parent resource group 800B comprising a plurality ofresource groups 801B is the target of data migration. The resource group801B inside storage apparatus 300, and the resource group 801B insidestorage apparatus 400 form a remote copy pair. Explanations in commonwith those of the second embodiment will be omitted so as to focus onthe points of difference.

The management server 200B of this embodiment differs from that of thefirst embodiment, and uses the volume attribute table 228A shown in FIG.25. The point of difference with the volume attribute table 228 shown inFIG. 10 is that information 2286 for specifying the partner in a copypair is added. That is, this volume attribute table 228A also managesassociation information between a plurality of volumes (remote copy pairinformation 2286).

In this embodiment, the migration-source storage apparatuses are storageapparatus 300 and storage apparatus 400. Further, themigration-destination storage apparatuses are storage apparatus 500 andstorage apparatus 600. The alternate storage apparatus is storageapparatus 700.

FIG. 26 is a flowchart showing a change migration destination processaccording to this embodiment. This flowchart comprises steps in commonto those in the flowchart described together with FIG. 20. Accordingly,if the explanation focuses on the points of difference with FIG. 20,when a failure occurs in either of the alternate storage apparatuses500, 600 initially set by the user (S91: YES), the management server200B determines whether or not an alternate volume candidate exists(S98A).

When there is no alternate volume candidate (S98A: NO), the managementserver 200B generates a copy volume 442A of the migration-source volume442 inside the migration-source storage apparatus 400 (S141). Then, themanagement server 200B finished the change of migration destinationprocess by overwriting the migration-destination volume informationinside the migration management table 226 to reflect the copy volume442A.

That is, when a failure occurs in storage apparatus 600 after aplurality of primary volumes 342 forming a remote copy pair have beenrespectively migrated to a plurality of volumes 542 inside storageapparatus 500, a local copy volume 442A of a secondary volume 442 isgenerated inside migration-source storage apparatus 400. Then, thecopy-pair relationship between the copy volume 442A and the primaryvolume 542 is re-set, and data migration processing is completed.

Furthermore, for the sake of expediting the explanation, a case in whicha copy volume 442A of a secondary volume 442 is generated inside anauxiliary storage apparatus 400 was described, but this embodiment isnot limited to this, and a constitution such that a copy volume of aprimary volume 342 is provided either inside a main storage apparatus300, or an auxiliary storage apparatus 400 is also acceptable.

This embodiment, which is constituted in this manner, also demonstratesthe same effects as the above-mentioned first and second embodiments. Inaddition, in this embodiment, the constitution is such that a copyvolume 442A, which is a local copy of the migration-source volume 442,is generated inside the migration-source storage apparatus 400, makingit appear that data migration has been completed. This makes it possibleto complete data migration processing even when an alternate storageapparatus cannot be found, thus enhancing usability.

Fourth Embodiment

A fourth embodiment of the present invention will be explained based onFIG. 27. In this embodiment, the functionality of the management server200C is provided inside storage apparatus 300. FIG. 27 is a schematicdiagram showing the overall constitution of a storage system of thisembodiment.

The management server 200C is provided inside storage apparatus 300.This management server 200C can manifest the same functionality as themanagement servers 200, 200A, 200B described hereinabove.

Further, in this embodiment, because the management server 200C isprovided inside storage apparatus 300, the storage management networkand host management network utilize a common network CN 13. Furthermore,the storage management network and host management network can also beintegrated in a constitution in which the management server 200C is notprovided inside storage apparatus 300.

Furthermore, instead of a constitution, which disposes the managementserver 200C in the migration-source storage apparatus 300, theconstitution can also be such that the management server 200C isprovided either inside the migration-destination storage apparatus 400or the alternate storage apparatus 500. Or, the constitution can also besuch that a management server 200C is provided in each storage apparatus300, 400, 500, and the management server to be utilized is selected asneeded from among these management servers.

This embodiment, which is constituted in this manner, also demonstratesthe same effects as the respective embodiments described hereinabove. Inaddition, in this embodiment, because the management server is embeddedinside a storage apparatus, the constitution of the storage system canbe simplified. Furthermore, the constitution can also be such that themanagement server is provided inside a host 100.

Fifth Embodiment

A fifth embodiment of the present invention will be explained based onFIG. 28. In this embodiment, when switching to an alternate storageapparatus, which a user selected beforehand, the constitution is suchthat user approval is obtained. FIG. 28 is a flowchart showing thechange migration destination process executed by the storage system ofthis embodiment.

This flowchart comprises steps common to those of the flowchartdescribed together with FIG. 20. Accordingly, if the explanation focuseson the points of difference with FIG. 20, in this embodiment, when thereis no failure in the alternate storage apparatus (S91: NO), instead ofswitching to an alternate storage apparatus right away, the managementserver queries the user as to the propriety of switching (S151), andwaits for approval from the user (S152). When approval from the user isnot obtained (S151: NO), data migration processing is canceled (S102).

This embodiment, which is constituted in this manner, also demonstratesthe same effects as those of the respective embodiments describedhereinabove. In addition, in this embodiment, since the user'sintentions are confirmed even when switching to an alternate storageapparatus specified ahead of time by the user, usability is enhanced. Itis possible to deal with a situation in which the user's expectationsdiffer from the initial mid-process control plan.

The present invention is not limited to the embodiments describedhereinabove. It will be understood by those having skill in the art thatvarious additions and changes can be made without departing from thescope of the present invention. For example, a person skilled in the artwill be able to combine the respective embodiments as needed.

In this embodiment, the constitution is such that the approval of theuser is requested when selecting one alternate storage apparatus fromany of the alternate storage apparatus candidates, or when switchingfrom the migration-destination storage apparatus to an alternate storageapparatus, but the constitution can also be such that the managementserver automatically carries out switching instead.

What is claimed is:
 1. A computer system comprising: a storage systemincluding a plurality of storage apparatuses, each providing volumes; ahost computer accessing the storage system via a network; and amanagement computer monitoring the plurality of storage apparatuses,wherein the management computer manages a resource group associated withmigration source volumes, wherein the management computer storesmigration management information which includes migration statuses ofthe migration source volumes to migration destination volumes, andidentifiers of alternate migration destination volumes corresponding tothe migration source volumes, and wherein, during migration of themigration source volumes to the migration destination volumes, themanagement computer: detects a certain status of the storage apparatusesaccording to the monitoring of the plurality of the storage apparatuses;queries a user to change migration destinations of the migration sourcevolumes, from the migration destination volume to the alternatemigration destination volumes; and changes migration destinations of themigration source volumes, from the migration destination volumes to thealternate migration destination volumes, if the management computerreceives instruction of change execution, wherein the managementcomputer receives a time period, selects the alternate migrationdestination volumes, based on loads of the volumes within the timeperiod, wherein the selection of the alternate migration destinationvolumes is executed before the migration of the migration source volumesto the migration destination volumes, wherein the management computerdisplays candidates of the alternate migration destination volumes insequence of low load within the time period, for the selection of thealternate migration destination volumes, wherein the plurality ofstorage apparatuses includes a parity group used by the volumes, andwherein the certain status of the storage system is an increased load ofthe parity group.
 2. A computer system according to claim 1, wherein thecertain status of the storage system is an increased load of thenetwork, and an increased load of volume.
 3. A computer system accordingto claim 2, wherein the change migration destination plans indicate acondition of a migration process for executing the nature of the controlprocess.
 4. A management computer managing a storage system including aplurality of storage apparatuses, each providing volumes, the managementcomputer comprising: a memory storing resource group information about aresource group associated with migration source volumes, and migrationmanagement information which includes migration statuses of themigration source volumes to migration destination volumes, andidentifiers of alternate migration destination volumes corresponding tothe migration source volumes; and a CPU configured to during migrationof the migration source volumes to the migration destination volumes:detect a certain status of the storage apparatuses according to themonitoring of the plurality of the storage apparatuses; query a user tochange migration destinations of the migration source volumes, from themigration destination volume to the alternate migration destinationvolumes; and change migration destinations of the migration sourcevolumes, from the migration destination volumes to the alternatemigration destination volumes, if the management computer receivesinstruction of change execution, wherein the CPU receives a time period,and selects the alternate migration destination volumes, based on loadsof the volumes within the time period, wherein the selection of thealternate migration destination volumes is executed before the migrationof the migration source volumes to the migration destination volumes,wherein the CPU displays candidates of the alternate migrationdestination volumes in sequence of low load within the time period, forthe selection of the alternate migration destination volumes, whereinthe plurality of storage apparatuses includes a parity group used by thevolumes, and wherein the certain status of the storage system is anincreased load of the parity group.
 5. A management computer accordingto claim 4, wherein the certain status of the storage system is anincreased load of the network, and an increased load of volume.
 6. Amanagement computer according to claim 4, wherein the change migrationdestination plans indicate a condition of a migration process forexecuting the nature of the control process.
 7. A computer programproduct stored in a computer readable medium for a management computermanaging a storage system including a plurality of storage apparatuses,each providing volumes, the computer program product comprising: a codecausing the management computer to store resource group informationabout a resource group associated with migration source volumes, andmigration management information which includes migration statuses ofthe migration source volumes to migration destination volumes, andidentifiers of alternate migration destination volumes corresponding tothe migration source volumes; and a code causing the management computerto, during migration of the migration source volumes to the migrationdestination volumes: detect a certain status of the storage apparatusesaccording to the monitoring of the plurality of the storage apparatuses;query a user to change migration destinations of the migration sourcevolumes, from the migration destination volume to the alternatemigration destination volumes; and change migration destinations of themigration source volumes, from the migration destination volumes to thealternate migration destination volumes, if the management computerreceives instruction of change execution, and wherein the computerprogram product causes the management computer to receive a time period,and select the alternate migration destination volumes, based on loadsof the volumes within the time period, wherein the selection of thealternate migration destination volumes is executed before the migrationof the migration source volumes to the migration destination volumes,wherein the computer program product causes the management computer todisplay candidates of the alternate migration destination volumes insequence of low load within the time period, for the selection of thealternate migration destination volumes, wherein the plurality ofstorage apparatuses includes a parity group used by the volumes, andwherein the certain status of the storage system is an increased load ofthe parity group.
 8. A computer program product according to claim 7,wherein the certain status of the storage system is an increased load ofthe network, and an increased load of volume.
 9. A computer programproduct according to claim 7, wherein the change migration destinationplans indicate a condition of a migration process for executing thenature of the control process.